Line data    Source code

       1              : #include "PuzzleImpl.h"
       2              : 
       3              : #include "Grid2d.h"
       4              : #include "LinewiseInput.h"
       5              : 
       6              : #include <algorithm>
       7              : #include <string_view>
       8              : namespace {
       9              : 
      10              : std::array<Grid2d<char>::Coord, 8u> constexpr stencil = {
      11              :     {{1, 0}, {0, 1}, {-1, 0}, {0, -1}, {1, 1}, {-1, -1}, {1, -1}, {-1, 1}}};
      12              : }
      13              : 
      14            1 : template <> std::string solvePart1<2025, 4>(std::string_view const input) {
      15            1 :   LinewiseInput linewise(input);
      16            1 :   Grid2d<char> grid = linewise.makeCharGrid2dWithGhostLayers(1, '.');
      17              : 
      18            1 :   uint64_t numAcessiblePaperRolls = 0;
      19          141 :   for (Grid2d<char>::Coord c{0, 0}; c.y() < grid.ySize(); ++c.y())
      20        19740 :     for (c.x() = 0; c.x() < grid.xSize(); ++c.x())
      21        19600 :       if (grid[c] == '@' &&
      22       100824 :           std::ranges::count_if(stencil, [&](auto const &d) { return grid[c + d] == '@'; }) < 4)
      23         1626 :         ++numAcessiblePaperRolls;
      24              : 
      25            1 :   return std::to_string(numAcessiblePaperRolls);
      26            1 : }
      27              : 
      28            1 : template <> std::string solvePart2<2025, 4>(std::string_view const input) {
      29            1 :   LinewiseInput linewise(input);
      30            1 :   Grid2d<char> grid = linewise.makeCharGrid2dWithGhostLayers(1, '.');
      31              : 
      32            1 :   uint64_t numPaperRollsRemoved = 0;
      33              : 
      34           58 :   for (bool haveRollsBeenRemoved = true; haveRollsBeenRemoved;) {
      35           57 :     haveRollsBeenRemoved = false;
      36         8037 :     for (Grid2d<char>::Coord c{0, 0}; c.y() < grid.ySize(); ++c.y())
      37      1125180 :       for (c.x() = 0; c.x() < grid.xSize(); ++c.x())
      38      1117200 :         if (grid[c] == '@' &&
      39      1894632 :             std::ranges::count_if(stencil, [&](auto const &d) { return grid[c + d] == '@'; }) < 4) {
      40         9173 :           grid[c] = '.';
      41         9173 :           ++numPaperRollsRemoved;
      42         9173 :           haveRollsBeenRemoved = true;
      43         9173 :         }
      44           57 :   }
      45              : 
      46            1 :   return std::to_string(numPaperRollsRemoved);
      47            1 : }